How to copy paste a node setup from one file to another
One option to help keep things organised is to create a Node Group from your setup.


Select all the nodes you want in your group
Ctrl G form a Node Group from them





Give the group a name by typing it into the field on its node. Click the shield  on the right. This will give the group a fake user, so it won't be garbage-collected and deleted when saving the source .blend, in the event that it's not being used by anything else in the file.


Now, in any other .blend, you can hit File > Append.. look up the source .blend file.. and the group will be found in the 'Node Tree' folder. Clicking it makes a local copy available under the  Shift A > Group listing in the Node Editor.

You can   Ctrl AltG un-group the node, locally.

(You can create libraries of any of the entities in a .blend file this way, to be linked or appended to other files)